The present invention relates to an image processing apparatus and more particularly to an image processing apparatus which is suitable for executing the arithmetic operation processing for image data stored in a work memory.
The image processing technology for processing image data obtained by an image pickup device has begun to be adapted to the monitoring system for detecting the invasion of a doubtful person or the abnormality and to the onboard system for supporting the safety travelling of a motorcar. In order to adapt the image processing technology to these systems, the small space and the low cost of an image processing apparatus are required. In order to realize the small space and the low cost, there is required the device of executing the image processing at high speed with the limited arithmetic operation ability of a CPU (Central Processing Unit) and the limited hardware physical superiority. As for the method of miniaturizing the image processing apparatus, for example, there is the method of adopting the single chip. The single chip is such that a CPU for executing the arithmetically operation processing, a ROM (Read Only Memory) for storing therein a program, a RAM (Random Access Memory) used as a work memory, and the functions required to construct the systems such as a network and a serial port are collectively integrated with each other into a package of one chip. By using this single chip, it becomes possible to realize the system, which is heretofore constructed by employing a plurality of devices, in one chip, which can contribute to the small space and the low cost of the image processing apparatus.
On the other hand, in order to execute the high speed image processing using a single chip, it is necessary to execute the image processing using a suitable memory within the single chip. This reason is that an access from a CPU to the external memory provided outside the single chip is generally slower than that to a local memory (work memory) provided in the inside of the single chip. For this reason, when executing the image processing using the external memory, it becomes difficult to provide the practical throughput. For example, with respect to the white line (traffic line or lane) recognizing function adopted in the on-board system, the recognition at the video rate is required and hence the high speed processing is required. But, in the case where the processing is executed using the external memory, it is difficult to fulfill the required performance. In addition, in the case of an environment resistance type single chip for use in the control or the like of motorcars, since the capacity of a memory in the single chip is small, an amount of data which can be processed at high speed is limited.
Then, as described in JP-A-2001-101396, there is proposed a method wherein image data stored in the external memory is sent to a local memory, which is integrated with a processor into one chip, through the DMA (Direct Memory Access) transfer to process the image data at high speed. In addition, as described in JP-A-6-4651, there is also proposed a method wherein only the data in an area which is used in the processing is transferred in order to execute the image processing at high speed. Each of those prior arts adopts the construction in which the image data is stored in the external memory and the necessary image data, when necessary, is transferred to the local memory in order to be processed.